|Subject:||Banded Stilt breeding plumage.|
|From:||Ian May <>|
|Date:||Mon, 01 Jul 2002 22:27:11 +0930|
Bill Jolly's comment about breeding plumage of Banded Stilt may be quite valid. My observations indicate that this enigmatic bird does indeed have a breeding plumage.
Having had the opportunity and good fortune to study large populations
of Banded Stilt at breeding sites such as Lake Callabonna, Lake Blanche,
Lake Torrens and Lake Eyre at various events from 1971 to 2000, I have
concluded that the plumage cycle of adults is not clear as some texts would
have us believe; that the breast band is mostly a breeding plumage and
that many birds do indeed lose their breast band post breeding.
Lake Callabonna 1974
At Lake Callabonna in early February 1974, within one week of widespread flooding about 50,000 Banded Stilt with plain breasts and with pink legs (indicating they were adults) appeared. These birds soon moulted acquiring breast bands over about 3 weeks After breeding nearby, the local population swelled to an estimated 100,000+ including a large number of recently bred juveniles (grey legs without breast bands). By May 1974, the ratio of fully banded adult birds present was about 60% the remainder were mostly unbanded juveniles.
Over the next several months many adults were observed with motley fading breast bands, the colour intensity diminishing over a period of about two months until disappearing completely. While the estimated local population of Banded Stilt remained about the same (100,000+), the ratio of unbanded birds present at Lake Callabonna increased to about 90% of the total. However determined by birds observed with pink legs, the ratio of adults (pink legs) remained at about 50%. The increasing number of plain breasted birds correlated to the number of adults observed losing their breast band post breeding.
Lake Eyre 2000
Observations made after the Lake Eyre breeding event in 2000 also suggest that most adult Banded Stilt moult their breast band post breeding. Soon after this nesting event, many adults with a partial breast band were observed returning to coastal areas with large numbers of juveniles. Not long after, at Penrice Saltfields near Adelaide, large numbers of mostly plain breasted Banded Stilt were present (30,000+) but the flocks preferred to segregate with juveniles flocking mostly in some areas and adults in others
Sometimes large flocks of Banded Stilt with complete breast bands are seen at coastal sites in South Australia when local conditions are not suitable for breeding. Sometimes this coincides with monsoon rain depressions or inland downpours occurring elsewhere within their range. At other times many of the birds have no visible breast band but more perplexing are observations suggesting that about 10%, probably older birds, may permanently retain a band.
Non breeding plumage may also be indicated when a large ratio of plain breasted Banded Stilts are observed during extended periods of widespread drought when a low ratio of juveniles would be expected. At such times, most of the plain breasted Banded Stilt are probably adults having moulted their breast band during extended periods of breeding inactivity.
In regards to a recent comment that plain breasted Banded Stilt have
been found nesting, occasionally an adult without a breast band is seen
to enter a colony and attending a crèche of departing chicks shortly
after a mass hatching occurs. Occasionally they are seen to interact
or clash with fully banded birds that are incubating. However of
the thousands of nests observed at various colonies, I have not observed
any plain breasted Stilt incubating or attending a nest. When it
does happen it would be an exception.
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